Low elongation set spandex filaments and process for the preparation thereof



United States Patent U.S. Cl. 264-405 4 Claims ABSTRACT OF THE DISCLOSURE Process for the preparation of spandex filaments of temporarily lowered elongation characterized in that spun filaments of a polyurethane elastic polymer by dry spinning are subjected to a heat treatment to reduce the solvent content remaining therein to no more than 0.5% by weight, the obtained filaments being further subjected to drawing, heat setting, cooling and shrinking operations.

This invention relates to a process for the preparation of spandex filaments of which elongation is temporarily lowered.

Heretofore, spandex or rubber filaments offered great difliculty for proper tension control during their posttreatments such as spinning, knitting and weaving because of their very high elongation of above 300%, normally even higher than 500%.

As a means to overcome this difficulty, a process was proposed in which elastic fibers are coated with a watersoluble polymer such as polyvinyl alcohol and set, but satisfactory setting effect cannot be thereby achieved. There is still another process proposed which comprises mix-spinning water-soluble polyvinyl alcohol or a non elastic polymer which is soluble in organic solvents with an elastic polymer, drawing the resultant mixed fiber to impart thereto a fixed elongation, making therefrom such products as knit or woven goods or semi-products as filaments or mixed yarn by suitable posttreatments and thereafter dissolving oif the non-elastic polymer so that the products should exhibit the elastic characteristics inherent in the elastic fiber. However, this process has its drawbacks such as complicated spinning step, difficulty for satisfactorily complete removal of the non-elastic polymer in the dissolving step, deformation caused in the section of the elastic fiber after removal of the non-elastic polymer, and high production cost.

Previously we proposed a process effective for imparting a low elongation, by drawing the filaments containing more than 0.5 wt. percent of the solvent still remaining therein immediately following the spinning step. Although low elongation set spandex filaments are obtained by the above drawing treatment of the solvent-containing spun filaments in accordance with the above process, permanent deformation is conspicuous in the resultant filaments which do not entirely recover their characteristics as the high elongation spandex filaments possessed before the drawing, at the stage of shrinking of the products prepared from the filaments such as yarn, knit or woven goods. For example, a polyurethane spun filament containing 1.0 wt. percent of dimethylformamide having an elongation of 430% was given a lower elongation of 110% when drawn by 3 times, but when the same was subsequently treated for minutes in 100 C. water free of tension, its elongation became 265%, thus failing to regain the elongation possesed before the drawing step. Again when the spun filaments contain a large volume of the solvent, high temperature drawing tends to cause filament breakage, while relatively low temperature drawing makes the drawing control insufiicient when the drawing speed is high.

We therefore engaged in further researches to find that polyurethane spandex shows behaviours close to one point drawing different from rubber, the tendency being particularly conspicuous in the polyurethanes prepared with a low molecular diol serving as the chain extender, compared with the polyurethanes prepared with other chain extenders such as hydrazin, diamine or water. Furthermore it is found that the tendency is enchanced under elevated temperatures. And, according to the invention the said polyurethane showing the behaviours of one point drawing for which a low molecular diol is used as the chain extender is found to possess the property to form far better spandex filaments of temporarily lowered elongation intended by the invention, compared with such polyuethanes prepared with other chain extenders, e.g., water, diamine and hydrazin. Still in addition We found substantially complete removal of solvent from the polyurethane filaments before the drawing to be highly effective for the preparation of the spandex filaments of which elongation is temporarily lowered. Those discoveries led us to the present invention.

Accordingly the object of the invention resides in the preparation of the spandex filaments of excellent properties and furthermore having an elongation temporarily lowered to around by the process which comprises dry spinning a spinning solution of a polyurethane elastic polymer in a heated spinning column and preparing spandex filaments having high elongation similarly to conventional spandex filaments, substantially completely drying the solvent in the subsequent drying step, drawing the filaments, heat setting the spandex filaments under tension, further cooling the same to at least below 50 C. and thereafter shrinking the same by 5-15 of the original length.

In the invention, a particular care should be taken to secure a sufiicient drying until the amount of the solvent remaining in the filaments after spinning and before drying is reduced to no more than 0.5 wt. percent to the filaments. Because, in case filaments containing more than 0.5 wt. percent of solvent are subjected to drawing, heat setting, cooling and thermal shrinking in accordance with the invention, admittedly fibers having an elongation of around 100% are obtained which, however, fail to perform sufficient shrinkage during the heat treatment at around 100 C. free of tension and consequently cannot regain the high elongation possessed before the drawing. For instance, a dimethylformamide solution of a polyurethane elastic polymer prepared from the three components of polyethylene propylene adipate (ethylenezpropylene copolymerization=9:l), 4,4-diphenylmethane diisocyanate and ethylene glycol (molar ratio=l.0:5.0:4.0) was dry-spun, and the resultant filaments having an elongation of 435% and a dimethylformamide content of 0.8 wt. percent were drawn, heat set, cooled and thermally shrunk in accordance with the process of this invention. Thus prepared fiber had an elongation of 118%, but when treated in 100 C. water for 10 minutes free of tension, it came to have an elongation of only 277% The temperature employed for drying of the solvent in accordance with the invention should be above boiling point of the solvent but no higher than 200 C. With the drying temperature below boiling point of the solvent, drying efiiciency is poor, and such high temperatures exceeding 200 C. should also be avoided because at the temperatures close to the melting point of the filaments fusion among the mono-filaments tends to take place.

Again the drawing temperature in accordance with the invention should be within the range of 80150 C., preferably 120150 C. Because, at temperatures below 80 C. the desired high speed drawing is inoperable, while at above 150 C. ideal one point drawing cannot be achieved, causing an uneven drawing effect. Furthermore, the draw ratio should be 26 times the original length of the filaments, for the reason that at a draw ratio less than 2 fibers of sufficiently lowered elongation cannot be obtained even after the heat setting, cooling and thermal shrinkage in accordance with the invention, and on the other hand with high draw ratios exceeding 6 and approaching the breaking point of the fibers, degradation in strength properties of the fibers is invited.

The heat setting temperature should range 150200 C., preferably 160180 C. Heat setting at below 150 C. could achieve the intended effect with prolonged setting time when the drawing temperature was below the said level, but such is not an industrially recommendable procedure. Once again temperatures exceeding 200 C. being close to the melting point or" the filaments, setting at such high temperatures tends to cause objectionable fusion among the monofilaments even within a short time.

Normally the heat setting in the order of 215 seconds can achieve the intended result.

Again in accordance with the invention it is necessary to cool the heat set filaments at below 50 C., preferably to room temperature, to stabilize the shrinking portions of the filaments formed when they are freed from tension, which were not heat set in the preceding step, and thereafter to shrink the filaments by 15% of the original length thereof. The purpose of this last shrinking is to prevent the occurrence of non-uniformity in properties of the products such as non-uniform denier and strength distribution when the elastic fibers of the invention are, for example, mix-spun, combined or subjected to other treatments with non-elastic fibers, such inuniformities being caused by the shrinkable portions present in the elastic fibers. In this shrinking step, the shrinkage should be by 5-15% of the original filament length. With a shrinkage less than 5%, substantial shrinking effect is hardly obtainable although the purpose of temporary fixing of elongation may be achieved. Whereas, when it exceeds the treated filaments are given an elongation of above about 150% to render the temporary fixing of the elongation ineffective. The shrinking can be performed between two rollers of different rotation speed at room temperature or with heating. In case of heating, incidentally, still the temperatures of the rollers should be at below 50 C.

Thus in accordance with the invention there is an advantage that even when the drying, drawing, heat setting, cooling and shrinking steps are performed as a continuous series to the spinning step, still low elongation set spandex filaments of uniform quality and even elongation distribution as desired can be obtained.

The spandex filaments thus prepared having an elongation of around 100120% and a tenacity of about 2.0 4.0 g./d. of the invention can be mix-spun, knit or woven with non-elastic fibers such as nylon and polyester using ordinary equipments for mix-spinning, knitting or weaving, without requiring the complicated tension control machine employed with conventional spandex filaments processing. Thus obtained knit or woven goods as they are fail to exhibit sufiicient elasticity due to the low elongation of the material spandex filaments, but upon allowing the products to sufiiciently shrink by heating the same to above 90 C., preferably about 100-150" C., so that the spandex filaments may regain the high elongation originally possessed before the drawing and heat setting, products having excellent elastic characteristics are obtained.

The invention now will be explained as to an embodiment for working the invention.

The spinning solution of a polyurethane elastic polymer of the invention is fed into a spinning head by means of a gear pump and extruded into a heated spinning column through which a heated gas is passed, from a nozzle in the spinning head. The filaments whereby formed contain about 4 wt. percent to the spun filaments of the solvent remaining therein when they leave the spinning column. The same are then led to godet rollers via oiling rollers and guides. The filaments thus containing about 4 wt. percent of the solvent are further well dried by means of heated Nelson rollers for drying to have the remaining solvent content reduced to no higher than 0.5 wt. percent. Thereafter the filaments are drawn between two rollers and heat set by means of heat setting Nelson rollers, followed by cooling by means of cooling rollers which are not heated but maintained at room temperature. The filaments are then slightly shrunk between two rollers and taken up onto a take-up machine.

As the polyurethane elastic polymers useful for the invention, block copolymers consisting of the following three components are employed: polymer diol of melting point no higher than 60 C. and molecular weight ranging SOS-5,000, preferably 800-3,000, and having terminal hydroxyl radicals; aromatic diisocyanate; and low molecular diol of molecular Weight ranging 50-200.

Specific examples of such polymer diol having terminal hydroxyl radicals include: polyethylene adipate, polyethylene propylene adipate, polybutylene adipate, polyhexamethylene adipate, polyethylene butylene adipate, polycaprolactam, polytctramethylene glycol, polypropylene glycol and polyethylene glycol.

As the aromatic diisocyanate, 4,4-diphenylmethane diisocyanate, 3,3,5,5'-tetramethyldiphenylmethane-4,4-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and the like are employed.

While any diol having a molecular weight ranging 50- 200 may be used as the chain extender, for example ethylene glycol, 1,4-butanediol, 1,6-hexanediol and the like are preferred.

The polyurethane elastic polymers contemplated in the invention are prepared from aforesaid three components, viz., high molecular polymer diol, aromatic diisocyanate and low molecular diol. They may be prepared in accordance with accepted practices. One of the known means for their preparation comprises reacting a polymer diol with an aromatic diisocyanate to form a prepolymer in which the terminal radicals of the polymer diol are isocyanate group, adding thereto each suitable amount of the aromatic diisocyanate and a low molecular diol to form a polyurethane block polymer. It is also possible to mix the three components from the start and react them. Furthermore, those reactions may be performed in a solvent such as dimethylformamide, dimethylsulfamide or methyl isobutyl ketone, in the presence of a catalyst.

Those polyurethane elastic polymers are the optimum starting materials for the spandex filaments of temporarily lowered elongation.

As the spinning solutions, those prepared by dissolving the above polyurethane elastic polymers in suitable solvents such as dim-ethylformamide, dimethylacetamide, tetrahydrofurane and dimethylsulfoxide are used.

Hereinafter the invention will be explained with reference to the working examples.

EXAMPLE 1 The three components: polyethylene propylene adipate (ethylene:propylene copolymerization ratio=9:1) having a molecular weight of 2,000 and terminal hydroxyl radicals; 4,4-diphenylmethane diisocyanate; and ethylene glycol were mixed at the molar ratio of 1.0:5.0:4.0, and the mixture was reacted in methyl isobutyl ketone at C. for 4 hours in the presence of dibutyl tin dilaurate as the catalyst. After completion of the reaction, methyl isobutyl ketone was removed from the system by vacuum drying, and whereupon powdery polyurethane elastic polymer was obtained. To the same polymer a composition consisting of 2.0 Wt. percent to the polymer of TiO 2.0 wt. percent of 4,4'-butylidene bis(3-methyl-6-tertiary butyl phenol), 0.5 wt. percent of acetic anhydride and 0.5

wt. percent of p-(lauryl thio-) ethyl alcohol was added, and the system was dissolved in dimethylformarnide to be made into a spinning solution of 30% concentration. The solution was fed, after debubbling, into a spinning head heated to 100 C. under an elevated pressure, and

and could not recover the high elongation after the shrinking treatment.

Again frequent filament breakage was observed during the drawing, and even when the drawing temperature was gradually lowered, the drawing control or stability was extruded through a nozzle having 0.2 mm. holes much inferior compared with the case of the invention. into a spinning column through which heated nitrogen was passed at the rate of 2 m. /hr. (calculated as 30 C.). The TABLE 2 spinning column was maintained at 180 C. in the vicinity Sample drawn of the nozzle, 300 C. at the top and 200 C., at the mid- 10 with 3.0 wt. The same samdle and lower portions. ggggjglfg if gf gggi The filaments thus spun had a remaining solvent con- P t heat set, cooled for minutes tent of about 5.0 wt. percent to the weight of the filaments rope y and Shrunk free ftensln containing the solvent immediately after they left the sping erdL 45 77 ning column. Continuously to the spinning step, the fila- 15 f. 1 1 ments were dried for 5 seconds on Nelson rollers heated g sfl o iu ua to 170 C. and driven at the rate of 350 m./min. Where- ;;35gggggfiflggpggtygig gg upon the solvent content of the filaments was reduced to f i 99 93 0.31 Wt percent. siglnntkage in 100 C.water (Per- 43 2 1 1 Continuously to the above drying, the filaments were 22 1 sgt ti naidistsgdid' drawn by 3.5 times at 150 C., and heat set for 1.5 secijff R?{*1 ffff ff1 6,6 M onds on heat setting rollers heated to 170 C. and driven at the rate of 1,225 m./min. and for 2.0 seconds on heat N th f d d f th setting rollers heated to 180 C., followed by cooling 5 proper g i Eprepalie 5 for 1.2 seconds on cooling rollers driven at the rate of 2 amems O tame m a (We Xamp e W 6 1,225 m./min. Then the filaments were shrunk by 10% 6 3 55 S 1 d f d by making the speed of the take-up roller (15 c.) 1,100 ti f g f i Yarn m./n1in. Filament breakage scarcely took place during the th WOO i P0 i i O g t operation over tens of hours, and drawing control was exan 6 Same mlxe yarn W1 6 Span ex amen S o cellenfly maintained Example 1 as the weft. The spandex filament was used The properties of the spandex filaments obtained thus in at the ratio of one thread to 3 Strands 9 the mlxed y accordance with the subject invention are given in Table The Weavmg w operable employing conventlonal 1 below, from which it can be understood that the product g i g f ahspeclal t is characterized by its low elongation, high tenacity, high t i a g ave i g g Youngs modulus and surprisingly great elasticity com- 6.011 e an W1 0 e a me S pared with conventional Spandex filaments Also from l1ttle elasticity as woven, but when SUbJCCtCd to a serles of Table 1 it can be understood that the low elongation set post'treatmlcnts compnsing rekixation m hot .Water to spandex filaments return to the conventional spandex filag: r??? i i g 9 3" ments of low tenacity and high elongation as they were 3 8 gg g j before the drawing and heat setting steps, when subjected S f 1 or .Secon s ry to a shrinking treatment in hot Water. heat to ach1eve dimensional stabil ty and dyemg step free of tensron, an elastic woven fabric of even surface was TABLE 1 obtained.

The same sam- Thus the elastic fabric in which the spandex filaments ggfifi fg gs t ggg of the invention were used showed an elasticity of 30% this for 15 minutes and an elastic recovery of 94% when elongated by 20%. Pr p inventlon free tenslm In contrast, the fabric prepared in the similar manner ex- Denier (d.) 42 79 cept using the spandex filaments containing 3.0 wt. pergfg g%g g 3; cent of the solvent showed in an elasticity of only 22%.

Y dulus: tenacity at 107 elonatlttt i/h .i .14 0.04 EXAMPLES 24 Elastic recovery after elongation 102 6 stffifiiffgt h'ttt' e".tstazruaasit i 54.0 2. 3 Example 1 was repeated except that the heat setting Sh s g g g tg igggg sm air 7 2 0 2 conditions were varied each time. The properties of the a mom emper resultant spandex filaments are given in Table 3.

TABLE 3 Heat setting condition Properties Shrinkage after Elongation of the Heat Heat Youngs modu- Shrinkage one month standsample after shrinking setting setting lns: tenacity at in 0. ing in air at room treatment for 12 min. temp. tlme Denier Tenacity Elongation 10% elongation water tem erature in 100 0. water free 0.) (second) (d.) (g./d.) (percent) (g./d.) (percent) percent) of tension (percent Control 2 .1 100 20 62 1. 75 221 0. 0s 25 34 450 Control 3 140 15 49 1. 91 0.08 as 20 405 Example2 160 s 44 2. 41 0.11 54 15 ass Example3 mo 5 41 2. ss 103 0.12 55 s 370 Example4 190 3 42 2. 73 107 0.11 53 9 375 Control Thus with the heat setting temperature of below For comparison, the drying was insufliciently performed leaving 3.0 wt. percent of the solvent in the same filaments which were subsequently drawn, heat set, cooled and shrunk in the same manner as above. The properties of the resultant spandex filaments are given in Table 2. As can be seen, the control filaments failed to show the high elasticity of the spandex filaments of this invention,

C., sufficient heat setting efiect cannot be obtained. Of course at the temperature below 150 C. still satisfactory 70 result could be obtained with prolonged setting time if the drawing temperature is also below 150 C., but such is not industrially recommendable. Particularly, when the spinning step is immediately followed by high speed processing, such prolonged treatment is not practical from the point of equipments.

Accordingly the heat setting temperature should be no lower than 150 C. in order to perform the heat setting of the invention with good etficiency.

EXAMPLE A polyurethane elastic polymer synthesized by reacting polycaprolactam having a molecular weight of 1,700 and terminal hydroxyl radicals with 4,4-diphenylmethan-e diisocyanate and ethylene glycol at the molar ratio of 1.0:5.0:4.0 was thoroughly dried, drawn, heat set, cooled and shrunk in the similar manner as described in Example 1. Thus prepared spandex filaments (40 deniers) showed a tenacity of 2.71 g./d., an elongation of 98% and a shrinkage in 100 C. Water of 52%. When the same was further shrunk under the same shrinking conditions evployed in Example 1, its elongation increased to 366%. On the other hand, filaments similarly prepared from a polyurethane elastic polymer obtained by reacting a prepolymer of polytetramethylene glycol having a molecular weight of 2,180 and 4,4'-diphenyimethane diisocyanate with ethylene diamine as the chain extender failed to exhibit sutficient low elongation set effect.

EXAMPLE 6 A dimethylformamide spinning solution (28% concentration) of a polyurethane elastic polymer-obtained by reacting the following three components, i.e., polyethylene butylene adipate having a molecular weight of 1950 and terminal hydroxyl radicals (ethylenezbutylene copolymerization ratio=8:2), 2,6-tolylene diisocyanate and 1,4butanediol, mixed at the molar ratio of 1.5:4.5:4.0 was dry-spun into a spinning column similar to that employed in Example 1, and thereby spun filaments having a remaining dimethylformaniide content of 4.5 wt. percent were obtained. After standing in a room of 20 C. for 10 hours, the filaments were dried on Nelson rollers of 175 C. driven at a rate of 300 m./min. for 8 seconds to have a reduced dimethylformamide content of 0.37 wt. percent. Thereafter the filaments were drawn by 4 times between two rollers heated to 135 (3., heat set on heat-setting rollers of 180 C. which were driven at a rate of 1200 m./min. for 6 seconds, cooled to about 2223 C. on cooling rollers of 20 C. driven at a rate of 1200 m./min. for 3 seconds, and shrunk by 10% as they were taken up onto a take-up roller of 20 C. driven at a rate of 1080 m./min. Thus obtained spandex filaments having a denier of 38 had a tenacity of 2.60 g./d. and an elongation of 80%. Whereas the same filaments, after the subsequent treatment in 100 C. water for 12 minutes free of tension, had a tenacity of 1.13 g./d. and an elongation of 390%, thus returning to the conventional spandex filaments of low tenacity and high elongation as they were before the treatments of the subject invention.

In contrast, the spandex filaments prepared under exactly same conditions to the above except that the 1,4- butanediol as the chain extender was replaced by hydrazine showed at 40 deniers a tenacity of 1.73 g./d. and an elongation of 340%, thus showing no low elongation set effect.

EXAMPLE 7 A dimethylacetamide spinning solution (32% concentration) of a polyurethane elastic polymer obtained by mixing and reacting the three components of polyethylene butylene adipate having a molecular weight of 1950 and terminal hydroxyl radicals (ethylene:butylene copolymerization ratio=8:2), 4,4-diphenylmethane diisocyanate and ethylene glycol at a molar ratio of 1.0:5.0:4.0, Was dry-spun into a spinning column similar to that employed in Example 1, and whereby spun filaments having a remaining dimethylacetamide content of 3.3 wt. percent were obtained. Continuously to the spinning step, the filaments were dried on Nelson rollers heated to 175 C. and driven at a rate of 330 m./min. for 5 seconds, to be given a reduced dimethylacetamide content of 0.33 wt.

percent. Then the filaments were drawn by 3 times between two rollers heated to 145 C., heat set on heat setting rollers of 185 C. driven at a rate of 990 m./min. for 7 seconds, cooled on cooling rollers of 25 C. driven at a rate of 990 m./min. for 5 seconds, and further shrunk by 5% as they were taken up onto take-up rollers of 20 C. driven at a rate of 940 m./min. Thus obtained spandex filaments had a denier of 35 and an elongation of 101%. When the same was further subjected to a shrinking treatment for 10 minutes in C. Water free of tension, the filaments showed an elongation of 415%, thus exhibiting excellent elastic recovery.

EXAMPLE 8 A spinning solution of 30% concentration was prepared by dissolving the powdery polyurethane elastic polymer of Example 1 in dimethylacetamide instead of dimethylformamide. The same was subsequently spun under the same conditions employed in Example 1 and continuously thereafter dried for 7 seconds on Nelson rollers at 180 C. The dimethylacetamide content of the resultant filaments was, to the filaments, 0.41% by weight. The filaments were thereafter treated under the same drawing, heat setting, cooling and shrinking conditions as of Example 1, giving spandex filaments of low elongation (elongation of 40 denier spandex filaments:87%), high tenacity (2.70 g./d.) and high Youngs modulus (tenacity at 10% elongation=0.2 g./d.).

When the same spandex filaments were treated in 100 C. water for 8 minutes free of tension, its elongation became 410%. Thus the product showed an excellent low elongation set effect.

For comparison, the above procedures were repeated except that the spun filaments still containing 0.75 wt. percent of dimethylacetamide were treated, yielding spandex filaments of which elongation was The same filaments, after 8 minutes treatment in 100 C. water free of tension, had an elongation of 283%, thus failing to regain the elongation of 413% possessed before the drawing.

We claim:

1. Process for the continuous preparation of spandex filaments having a temporarily lowered elongation of less than and a tenacity of 2.0-4.0 g./den., characterized in that a spinning solution of a polyurethane elastic polymer prepared from a polymer diol having a molecular weight of 5005,000, an aromatic diisocyanate and a diol having a molecular weight of 50-200, dissolved in an organic solvent of boiling point below 200 C. is dry spun and the resulting filaments are subjected to treatments comprising, in succession:

(1) drying the spun filaments at a temperature above the boiling point of the solvent but no higher than 200 C. to reduce the residual solvent content to no more than 0.5% by weight,

(2) drawing the filaments to 26 times their original length at a temperature of 80150 C.,

(3) heat setting the drawn filaments at a temperature of 200 C.,

(4) cooling the heat set filaments to a temperature below 50 C.,

(5) causing the filaments to shrink by 5-15% of their original length.

2. The process for the continuous preparation of temporarily low elongation set spandex filaments according to claim 1, in which the low molecular diol is ethylene glycol.

3. The process for the continuous preparation of temporarily low elongation set spandex filaments according to claim 1, in which the polyurethane elastic polymer is that obtained by the reaction of polyethylene propylene adipate having a molecular weight of 5005,000, 4,4- diphenylmethane diisocyanate, and ethylene glycol.

4. The process according to claim 1, in which the solvent is selected from a group consisting of dimethylformamide, dimethylacetamide, tetrahydrofurane and dimethylsulfoxide.

References Cited UNITED STATES PATENTS Clendening 5734 1 0 FOREIGN PATENTS 916,287 1/1963 Great Britain.

DONALD J. ARNOLD, Primary Examiner H. MINTZ, Assistant Examiner US. Cl. X.R. 

